Plant Identification: CLOSED: Mystery flower, 1 by SpiritSinger

SpiritSinger wrote:Found in south dakota, western half, mix prairie and badlands, soil is mostly clay. Plant grows close to ground, stems some six inches or so long and tend to lay more than stand. Flowers not clustered so much as loosely grouped. Branches bearing leaflets do not go all the way up but stop roughly halfway along main stem. This flower is fairly common here, where cattle graze. I am thinking it is a type of vetch but no matter how I search, I cannot find its exact species. And it is going to bug me until I do. So please help me identify it if you can. Thank you.